Cyanine dyestuffs



Patented Mar. 19, 1946 CYANHVE DYESTUFFS' John David Kendall, Ilford, England, assignor to Iliord Limited, Ilford, England, a company of Great Britain No Drawing.- Application February 16, 1942, Serial No. 431,166. In Great Britain April 7,

11 Claims.

This invention relates to the manufacture of dyestufis and particularly to the manufacture of dyestuifs capable of optically sensitising silver halide photographic emulsions.

According to the present invention dyestuffs are produced by condensing about three molecular equivalents of an alkyl or aralkyl quaternary salt of a heterocyclic nitrogen compound containing a reactive methyl or mono-substituted methyl group in the on or 7 position to the quaternary nitrogen atom with about one molecular equivalent of a compound of the formula:

where the groups R2 are hydrocarbon residue e. g. akyl, aryl or aralkyl groups. 1

The course of the reaction is believed to beas follows:

or as an alkyl or aralkyl sulphate quaternary salt by fusing the heterocyclic nitrogen base with the trithiocarbonate reagent and an alkyl or aralkylp-toluene sulphonte, or alkyl or aralkyl sulphate, thus converting the heterocyclic base to the corresponding quaternary salt in situ. Advantageously, in order to obtain the best yield the fused mass is heated with pyridine priOr to separation of the dyestuff. If the final dyestuif is required as a salt other than a p-toluene sulphonate it may be converted into such other salt by treatment with a solution of an appropriate alkali salt, e. g. potassium chloride, potassium bromide or potassium iodide.

Any of the known types of heterocyclic quaternary ammonium compounds containing the specified reactive methyl group previously described for use in the manufacture of cyanine dyes may be employed in the process of the present invention.

In this equation, D represents the residue of a heterocyclic nitrogen compound, R represents an alkyl or aralkyl group, R1 represents a hydrogen atom or an alkyl, aryl or aralkyl group, R2 represents an alkyl, aryl or aralkyl group, X represents an acid group (e. g. chloride, bromide, iodide, alkyl or aralkyl sulphate, p-toluene sulphonate or perchlorate) and n is nought or 1. In some instances the reaction does not proceed to the trinuclear stage as evidenced by the following examples and dinuclear products are obtained which contain a central SR2 substituent.

The reaction may be carried out by heating the quaternary salt with the trithiocarbonate reagent, preferably in the presence of a base and a solvent. A solution of sodium acetate in ethyl alcohol is suitable, or organic bases may be used, e. g. piperidine, triethylamine andtriethanolamine. 'Pyridine is of particular value in that it serves. as both base and solvent. I

Preferably. however, the dyestuff is'initially ob- Examples. are the substituted and unsubstituted thiazoles, oxazoles, selenazoles and their polycyclic homologues such as those of the benzene, naphthalene, acenaphthene and anthracene series; pyridine and its polycyclic holomogues such as quinoline and a and B naphthaquinolines; lepidines; indolenines; diazines; such as pyrimidines and quinazolines; diazoles (e. g. thio-f3/3'-diazole) oxazolines, thiazolines and selenazolines. The polycyclic compounds of these series may also be substituted in the carbocyclic rings with one or more groups such as alkyl, aryl," amino, hydroxy, alkoxy and methylene dioxy groups, or by halogen atoms.

In the foregoing formulae the groups R. and R1 may be alkyl groups and examples are the methyl, ethyl, propyl and higher alkyl groups, allyl and similar unsubstitued groups, or they maybe aralkyl groups, e. g. benzyl groups; R1 may be an aryl group, e. g. a pheny1 or naphthyl group.

The following examples illustrate the invention but are not to be regarded as limiting it in any way.

Example I vtained as a p-toluene' sulphonte quaternary salt 4.5 gms. of l-methyl benzthiazole, 5.7 gms. of

Example II Preparation of the dyestufL of the prqhgbjq formula: 1 l a v Q I I The process was carriedoutas in Example I using 4.3. girls. of quinaldine; 5;7igms. of methyl-p-tolu'ene's'ulphonate and5'1'.38; gms. of .dimethyl trithioearbonate. The product; wasobtained. as, a green dye melting at 273980..

Example III. Preparation of the cly e stgui fof the prohalole formula; 3Q

The process was carried out as ln Examp-1e I i a Example I Preparation of the dyestutf of the probable for ula: r "3 1 4 QHi SC Ba The process was carried out as in Example I'using 4.0 gmsi' of 'l-methyl benzoxazole, 5.7 gms. of methyl-p-toluenesulphonate and 1.38 gms. of dimethyl trithiocarbonate. The produt was obtained as an orange solid; melting at 278 C.

Example V Preparation of the dyestufi? of probable formula:

. methyl trithiocarbonate.

The prpcesswasearried out as in Example I using 4.5 gmsl of l fne'thyl benzthiazole, 6.0 gms. of ethyl p-toluene sulphonate and 1.38 gms. of dimethyl trithiooarhqnate. The product was obtained as a green dye having a melting point of .??Q.

E mple i pa at sn of heye t fi; o ro bl forrnula:

The processwas oarriedroutias in Examplel .using 6.0 gms. of l-methylloenzselenazole,v 6.0-gins. of ethyl-p-toluene ,sulphonate. and 1.38' gms. of di- The product was. ob, tained as a brownish coloured dye softening at 148 C. and melting at 22 0f? C,

' Example VII Preparation of the dyestufi' of probable formula:

The process was arried out as in Exarnple I using tained as a green dye hailing a melting point of Preparation of the dyestnij o flfl probable lw i- .v V.

l 'lheproeesslwas icaniedout. as:in;Examp1e I using Ezvample IX Preparation of the dyestuff of probable formula:

S CH=O\N/ 'SCH:

6.0 gms, of l-methyl-fl-naphthiazole and 6.0 gms. of ethyl-p-toluene sulphonate were fused for four hours at 180 C. To the fused product was then added 1.38 gms. of dimethyl trithiocarbonate and the mixture re-fused for three hours at 140 C. The fused mass was then mixed with 30 cos. of pyridine and boiled for forty minutes, after which the mixture was poured into an aqueous olution of potassium iodine. A tar-like mass separated out, which, after triturating with benzen followed by recrystallisation from methyl alcohol, yielded the product as a dark green dye melting at 229 C.

Many of the dyestuffs produced according to the present invention are valuable sensitising dyes for photographic silver halide emulsions. Thus, for example, incorporated in a gelatin silver iodobromide emulsion, the product of Example I extends the sensitivity of the emulsion to about 6800 A., the product of Example III extends the sensitivity of the emulsion to about 6600 A. with a maximum at about 6100 A, the product of Example VII extends the sensitivity of the emulsion to about 6600 A. with a maximum at. about 6000 A. and the product of Example VIII extends the sensitivity of the emulsion to about 6600 A. with a maximum at about 6100 A.

The dyestuffs may be employed for sensitising any type of gelatino silver halide emulsion, e. g. silver chloride, silver bromide, ilver chlorobromide and silver iodobromide emulsions. The quantity of dyestuff employed for sensitising will, of course, vary with the particular dye and the purpose for which the emulsion is intended. In general, for a typical emulsion containing the equivalent of 2% silver calculated as metal, the proportion may range between 250-1250 cos. of a 1 in 2,000 solution per litre of emulsion.

What I claim is:

1. A process for the manufacture of dyestuffs which comprises condensing, by heating together, about three molecular equivalents of a compound selected from the group consisting of alkyl and aralkyl quaternary salts of heterocyclic nitrogen compounds of the type commonly employed in cyanine dyes containing in one of the a and 7 positions to the quaternary nitrogen atom a reactive group selected from the group consisting of methyl and mono-substituted methyl groups, with about one molecular equivalent of a compound of the general formula:

s o sm where the groups R2 are hydrocarbon radicals.

2."A process for the manufacture of dyestuffs:- which comprises condensing, by heating together,

about three molecular equivalents of a heterocyclic nitrogen compound of the type commonly employed in cyanine dyes containing in one of the a and 1 positions to the heterocyclic nitrogen atom a reactive group selected from the group consisting of methyl and mono-substituted methyl 1 roups, with-about one molecular equivalent ofa compound of the general formula:

C-SRa where the groups R2 are hydrocarbon radicals, in in the presence of sufilcient of a salt selected from the group consisting of alkyl and aralkyl salts to convert the said heterocyclic compound to a quaternary nitrogen salt.

3. A process for the manufacture of dyestuffs which comprises condensing, by heating together, about three molecular equivalents ofa heterocyclic nitrogen compound of the type commonly employed in cyanine dyes containing in one of the a and 'Y ositions to th heterocyclic nitrogen atom a reactive group selected from the group consisting of methyl and mono-substituted methyl groups, with about one molecular equivalent of a compound of the general formula:

where the groups R2 are hydrocarbon radicals, in the presence of sufiicient of an alkyl-p-toluene sulphonate to convert the said heterocyclic compound to a quaternary nitrogen salt.

4. A process for the manufacture of dyestuffs which comprises condensing, by heating together, about three molecular equivalents of a heterocyclic nitrogen compound of the type commonly employed incyanine dyes containing in one of the a and 7 positions to the heterocyclic nitrogen atom a reactive group selected from the group consisting of methyl and mono-substituted methyl groups, with about one molecular equivalent of a compound of the general formula:

where the groups R2 are hydrocarbon radicals, in the presence of suflicient of a salt selected from the group consisting of alkyl and aralkyl salts to convert the said heterocyclic compound to a quaternary nitrogen salt, and completing the condensation by heating the reactants in the presence of a base.

5. A process for the manufacture of dyestufis which comprises condensing, by heating together, about three molecular equivalents of a heterocyclic nitrogen compound of the type commonly employed in cyanine dyes containing in one of the 0c and '7 positions to the heterocyclic nitrogen atom a reactive group selected from the group consisting of methyl and mono-substituted methyl groups, with about one molecular equivalent of a compound of the general formula:

s C SRz where the groups R2 are hydrocarbon radicals, inv

u phonat itocony rtithesaid heterocyclio com- Round to aquaternaryrnitrosen alt; .nd -co m,.-v. pletingthe condensation-byheatinethereactant inzthe presence of :abase.-

6; A process forv the; manufacture 10f. d fistufise which compr sicon n in i by-heafineiqcether; ahout'three-molecular equivalents of acomponnd; selected from the group consisting: of: alkyl; and;

ara-lkyl 1 quaternary. saltsaof a: polycyclic; .azole; .se 7

ith about one molecular: equi a entraccomrnoundof the-. en ral crmu az S32; wherethe groupsRz arehydrocarbon radicals.-

7'; A process for the manufacture of dyestuffs: which comprises condensing, by heating together, about three molecularequivalents of a polycyclic azole selected from the group consisting of oxazoles, thiazoles and=se1enazoles containing arc-- matic rings fused to the-azole rings and having in the a position to the heterocyclic nitrogen atoma reactive group selected from the group consisting of methyl and. mono-substituted methyl groups, with about one molecular equivalent of a compound of the general formula:

\SRQY where the groups'R -arehydrocarbon radicals; in thepresence of suificient'ofa salt selected from the group consisting of alkyl and aralkyl salts to convert the said polycyclic azoleto a quaternary nitrogen salt.-

8*; A process for the manufacture of dyestuffs which comprises condensing; by heating together; about three molecularequiyalents of--a compound selected from the group" consistingof alkyl and;

aral y-l. quaternary 'saltsofzhetemcyclic nitroscnr;v

compounds-oi the; type; commonly employed: in; cyanine dyes containing inione. of: the, wand 7': positions to:the: quaternary nitrogen atom- 3.131183."

2 active group selected from the group consisting;

where the groups R2 are hydrocarbon radicals, the condensation being efiectedin the presence of l a base.

9. Adyestufi of the formula:

I SCH:

1 cm 10. A dyestufi of the formula:

C QB. JOHN DA-VID 

